Fix use of uninitialized raw pointer in oilpan build.

Source/core/css/parser/CSSPropertyParser.cpp

Index: Source/core/css/parser/CSSPropertyParser.cpp
diff --git a/Source/core/css/parser/CSSPropertyParser.cpp b/Source/core/css/parser/CSSPropertyParser.cpp
index 067160cd49d4d0ef19a237fb652fcb84d5852e17..6ebf516f9c0f4acfb1afe0fc23d3646eed4bbce9 100644
--- a/Source/core/css/parser/CSSPropertyParser.cpp
+++ b/Source/core/css/parser/CSSPropertyParser.cpp
@@ -7248,9 +7248,9 @@ PassRefPtrWillBeRawPtr<CSSValueList> CSSPropertyParser::parseTransformOrigin()
 {
     CSSParserValue* value = m_valueList->current();
     CSSValueID id = value->id;
-    RefPtrWillBeRawPtr<CSSValue> xValue;
-    RefPtrWillBeRawPtr<CSSValue> yValue;
-    RefPtrWillBeRawPtr<CSSValue> zValue;
+    RefPtrWillBeRawPtr<CSSValue> xValue = nullptr;
+    RefPtrWillBeRawPtr<CSSValue> yValue = nullptr;
+    RefPtrWillBeRawPtr<CSSValue> zValue = nullptr;
     if (id == CSSValueLeft || id == CSSValueRight) {
         xValue = cssValuePool().createIdentifierValue(id);
     } else if (id == CSSValueTop || id == CSSValueBottom) {